1. Field of the Invention
This invention relates to a thermal print head used in thermal recording systems such as thermal printing, thermal transfer printing or thermal ink jet printing.
This invention also relates to a method of manufacturing the thermal print head in which a thin, fine glass film of a uniform thickness can be formed on a base.
Furthermore, this invention relates to an apparatus for manufacturing the thermal print head in which a base is passed through molten glass to form a glass glaze layer on the base.
2. Description of the Prior Art
A thermal print head usually has a group of heating elements and electrodes on a metal or ceramic base to which a glass glaze has been applied. An example of such a thermal print head is taught in Japanese Utility Model Laid-Open Application No. 57-193545. According to this disclosure, the thickness of the glass glaze should be approximately 100 .mu.m.
The method by which this disclosure teaches the glass coating should be applied to the surface of conventional thermal print heads includes dissolving fine glass powder in water or a binder, coating the surface of the base with this solution, and then baking it at high temperature in an infrared oven or gas furnace.
However, the conventional method has suffered from a number of drawbacks, in that faults such as pinholes were liable to occur in the glass coating, the glass film was too thick, and its adhesive strength was not great, so that it was liable to peel off. These factors shortened the life of the thermal print head.
Of course, melting glass in an electric furnace is also well known as taught in U.S. Pat. No. 3,524,918. However, nowhere in this reference is there any suggestion of using the furnace to apply glass glazes to print heads, or how the furnace could be modified to efficiently process elongated work pieces.